Coherence properties of quantum optical solitons in the normalized fun
damental soliton states are discussed in terms of the integrated two-p
oint field and intensity autocorrelation functions, which are the rele
vant quantities in the quantum description of soliton interference exp
eriments and in the Hanbury-Brown and Twiss experiment, respectively.
Both the spatial and the temporal correlation properties are considere
d. The correlation functions are shown to be stationary in general, wh
ich demonstrates the solitary behavior of quantum fundamental solitons
and indicates their stability in propagation. Explicit evaluation of
the correlation functions in some limit cases enables us to make compa
risons between the classical and the quantum-mechanical results. Condi
tions leading to the classical limit are derived and the intrinsic qua
ntum phenomena are identified. Of great importance is the contribution
of the momentum superposition, which can make the quantum results dif
fer significantly from the corresponding classical ones.